Method and device for transmitting/receiving data to/from base station in wireless communication system

Abstract

The present specification may provide a method for transmitting/receiving data in a wireless communication system, the method being performed by a terminal and comprising the steps of: transmitting, to one or more alternative base stations having an alternative link configured, an activation request message for requesting the activation of the alternative link into a signaling radio bearer (SRB) active state; receiving, from the one or more alternative base stations as a response to the activation request message, an activation response message comprising load status information of the one or more alternative base stations; on the basis of the load status information, determining a serving base station candidate for activating the alternative link into the SRB active state; and transmitting, to the determined serving base station candidate, an activation completion message indicating that the alternative link has been activated into the SRB active state.

The invention claimed is: 
     
       1. A method for transmitting and receiving data in a wireless communication system supporting a low latency service, the method performed by a user equipment (UE) and comprising:
 receiving, from a serving base station, information on a maximum number of alternative links 
 wherein based on the information on the maximum number of alternative links, a plurality of alternative links are established between (i) the UE and (ii) a plurality of alternative base stations,
 wherein the plurality of alternative links are a link that only a Signaling Radio Bearer (SRB) in an inactive state is configured without configuring a Data Radio Bearer (DRB), 
 wherein a serving link established between the UE and the serving base station is a link that both a SRB in an active state and the DRB are configured, and 
 wherein the SRB in the inactive state is kept to a sleep mode until the UE transmits a request message for a SRB activation for the SRB in the inactive state to the plurality of alternative base stations; 
 
 transmitting the request message to the plurality of alternative base stations when detecting degradation of the serving link, 
 wherein the request message includes an activation timer, and 
 wherein a radio resource configuration configured to the UE by an alternative base station is released based on the activation timer when an activation completion message is not received by the alternative base station until the activation timer expires; 
 receiving, from the plurality of alternative base stations, an activation message including load status information of the plurality of alternative base stations in response to the request message; 
 selecting a candidate serving base station among the plurality of alternative base stations, based on the load status information; and 
 transmitting the activation completion message to the candidate serving base station, 
 wherein the request message comprises a cause field indicating a reason of SRB activation, and 
 wherein the reason of SRB activation is radio link failure avoidance of the serving base station. 
 
     
     
       2. The method of  claim 1 , wherein the request message further comprises a synchronization information indicating a synchronization order among the plurality of alternative base stations, and
 wherein the activation message is transmitted according to the synchronization order. 
 
     
     
       3. The method of  claim 1 , wherein a synchronization order is a sequence of fast synchronization or a sequence of slow synchronization from the UE. 
     
     
       4. The method of  claim 1 , wherein the load status information is one of high, medium, or low state. 
     
     
       5. The method of  claim 1 , wherein the activation message further comprises configuration information related to configuring radio resources of the plurality of alternative base stations. 
     
     
       6. The method of  claim 1 , wherein the activation completion message comprises at least one of list information of other alternative base stations in SRB inactive state or alternative base station information indicating a candidate alternative base station for setting up an alternative link. 
     
     
       7. The method of  claim 6 , further comprising:
 receiving, from the candidate serving base station, an RRC (Radio Resource Control) connection reconfiguration message including C-RNTI (Cell-Radio Network Temporary Identifier) assigned to the UE by the candidate alternative base station to which an alternative link for the UE is established. 
 
     
     
       8. The method of  claim 1 , wherein the request message further comprises timer information representing a timer for discovering the radio link failure. 
     
     
       9. The method of  claim 8 , further comprising:
 starting the timer, when degradation of radio link quality of the serving base station is detected, 
 wherein the request message is transmitted before starting the timer; and 
 transmitting an inactivation request message requesting inactivation of a SRB of a candidate serving base station to the candidate serving base station, when quality of the radio link is recovered before the timer is completed. 
 
     
     
       10. The method of  claim 1 , wherein load status of the candidate serving base station is the lowest one among the plurality of alternative base stations. 
     
     
       11. A user equipment (UE) for transmitting and receiving data in a wireless communication system supporting a low latency service, the UE comprising:
 a communication unit configured to transmit and receive a radio signal to and from an external communication device; and 
 a processor functionally connected to the communication unit, 
 wherein the processor is configured to: 
 receive, from a serving base station, information on a maximum number of alternative links 
 wherein based on the information on the maximum number of alternative links, a plurality of alternative links are established between (i) the UE and (ii) a plurality of alternative base stations, 
 wherein the plurality of alternative links are a link that only a Signaling Radio Bearer (SRB) in an inactive state is configured without configuring a Data Radio Bearer (DRB), 
 wherein a serving link established between the UE and the serving base station is a link that both a SRB in an active state and the DRB are configured, and 
 wherein the SRB in the inactive state is kept to a sleep mode until the UE transmits a request message for a SRB activation for the SRB in the inactive state to the plurality of alternative base stations; 
 transmit the request message to the plurality of alternative base stations when detecting degradation of the serving link radio link, 
 wherein the request message includes an activation timer, and 
 wherein a radio resource configuration configured to the UE by an alternative base station is released based on the activation timer when an activation completion message is not received by the alternative base station until the activation timer expires; 
 receive, from the plurality of alternative base stations, an activation message including load status information of the plurality of alternative base stations in response to the request message; 
 select a candidate serving base station among the plurality of alternative base stations, based on the load status information; and 
 transmit the activation completion message to the candidate serving base station, 
 wherein the request message comprises a cause field indicating a reason of SRB activation, and 
 wherein the reason of SRB activation is radio link failure avoidance of the serving base station.